1. Field of the Invention
This invention relates to radiation meters, and in particular to radiation meters for measuring the intensity of incident radiation within a predetermined wavelength band against a background of incident radiation within other wavelength bands, for example broadband radiation.
2. Description of Related Art
Such meters are widely used in a number of applications by individual consumers, in industry, and in medicine. One example is in the silicon integrated circuit industry where high-resolution photolithographic processes depend on a source of ultra-violet radiation of known intensity. In order to distinguish between the incident UV radiation and the background wideband radiation, the meters presently used in such an application employ a filter which selectively transmits UV radiation to a UV-sensitive photo-detector. As both these items are quite expensive, this leads to the cost of such a meter being relatively high.